The invention concerns a suspension stop for a motor vehicle wheel as well as a method of measuring the vertical forces applied to a wheel associated with the chassis of a vehicle by means of such a stop.
Known stops conventionally comprise a fixed member intended to be secured to the vehicle chassis and a rotating member intended to be fixed with respect to rotation to the suspension spring.
In particular, the stops can comprise a bearing provided with a fixed top race, a rotating bottom race and rolling bodies disposed between the said races.
Thus the stops make it possible to connect the wheels to the chassis of the vehicle by means of suspensions and associated springs, leaving the wheels free to move angularly and withstanding the multiaxial forces due to the running conditions (acceleration, braking, the state of the surface, cornering, etc).
In particular, the vertical forces cause a variation in the compression of the spring and therefore a coiling of its turns on themselves, which gives rise to a rotation of the rotating member with respect to the fixed member.
Moreover, it is desirable to measure the forces suffered by the vehicle wheels, in particular for the requirements of a certain number of electronic assistance systems on the vehicle, for example intended for active safety, driving comfort (in particular suspension control) or a reduction in fuel consumption.
For this purpose, it is known how to directly measure the forces exerted by the road on the vehicle, these measurements being made either at the tyre or at the components of the wheel set. However, these measurement strategies have a certain number of limitations.
In particular, when the measurement is made on the tyre, which is a rotating component, there are posed problems of transmitting the signal in a fixed reference frame so as to be able to derive the modulus of forces therefrom, and this all the more critically since the signals are numerous and must be analysed in real time in order to be able to control the assistance systems.
Concerning the measurement on the wheel-set components, the main problem which is posed is that of the analysis of the signals in order to derive therefrom the modulus of forces respectively in the three directions in space. This is because the application of a transverse force to the bottom of the wheel creates a moment of tilt at the bearing which is due to the lever arm represented by the radius of the wheel. The effect of the transverse force will therefore be preponderant on the effect of the vertical force, which makes the exact determination of this vertical force difficult.